This invention relates to railroad crossing rail bed units of the type employed in constructing railroad crossings across highways and private roads.
As is well known, railroad grade crossings are subjected to heavy stresses caused by the cyclic compressing and resurgence of the crossing components with the passage of each locomotive and railroad car traversing the crossing. This causes loosening of whatever fixation means is employed to fix the rails in place. It also causes spalling and breaking away of the concrete and asphalt paving materials associated with the crossing. If the crossing structure includes wooden ties, the ties are squeezed between the tie plates and ballast with resultant deterioration and fragmentation. Still further, the repeated impacts cause the ties to subside into the underlying ballast so that they no longer support the rails properly.
These factors make necessary periodic reconstruction and repair of the crossing. During such reconstruction and repair, the crossing surface must be removed and salvaged, if possible; the ties must be renewed and re-tamped to their former elevation; and the surface must be restored, all at considerable expense. After a short time, the cycle repeats itself.
In my former patents, Harmon U.S. Pat. No. 3,317,137 and Harmon U.S. Pat. No. 3,892,356, modular railroad grade crossings are described which in large measure overcome the foregoing problems. However, there is need for a crossing having a cushioned action which in particular compensates for the above noted cyclic compression and resurgence of the crossing structure which is so damaging to the crossing components. It is the primary purpose of the present invention to provide such a cushioned crossing.
Other objects of the present invention are the provision of a cushioned railroad grade crossing which eliminates the use of wood ties; which is easily adapted to various track forms and sizes; which is anchored to the surrounding pavement; which has provision for the mounting of signal-operating electric circuits; and which has provision for introducing pressurized grout beneath the crossing if major crossing subsidence should occur.
Further important objects of the present invention are the provision of a cushioned, modular grade crossing which is of relatively low initial cost; which conforms to the highway geometry; which is smooth and of neat appearance; and remains in this condition during a long service life, with minimum maintenance.
The foregoing and other objects of the invention are accomplished by the provision of a modular railroad grade crossing which in essence comprises a base, preferably formed of cast concrete, with an elevated central section having a substantially flat upper surface at roadway level and a pair of opposite, depressed side sections having upper surfaces at substantially rail base level. On each side of the base, at the boundaries between the central and side sections, there are releasable rail-fixation means for releasably fixing a pair of rails to the base in substantially parallel relation to each other.
The fixation means comprise a plurality of rail fixation members arranged in rows, one row on each side of the base.
Each fixation member comprises broadly a connector underlying the rail, transversely thereof. The connector mounts a rail keeper on one of its ends and a releasable rail clamp on the other of its ends. A cushioning means such as a resiliently compressible pad is inserted between the keeper and the rail, and between the clamp and the rail. A running strip of compressible material underlies the rail. A cushioned rail mounting thus is provided which absorbs the recurring shocks of compression and resurgence accompanying each train passage. At the same time, the rails are efficiently fixated in the crossing so that the damage to the crossing components is kept at a minimum.